Usually, the cores of magnetic heads are made of ferrites. Where a high magnetic permeability should be obtained, a magnetic metal film is formed on the surface of such a ferrite core. If this magnetic film is directly formed on the ferrite core, the following various problems take place:
(1) The magnetic metal film adheres to the core with a small force and, therefore, the film often peels off during the manufacture of the magnetic head.
(2) During thermal treatment, the ferrite reacts with the magnetic metal film, giving rise to a magnetically deteriorated layer. As a result, a pseudo gap is created. Thus, a pseudo output is produced as shown in FIG. 5.
(3) Soft magnetic characteristics intrinsic in the magnetic metal film cannot be obtained.
In order to solve these problems, the formation of an intermediate film, called a diffusion preventive film, between the ferrite core and the metal film may be contemplated. The above-described problems may be solved by the use of this intermediate film. However, this urges the use of an additional material, which increases the manufacturing costs and the number of the manufacturing steps.